chore: import upstream snapshot with attribution

python/tvm/backend/_autoload_backends.py

@@ -0,0 +1,88 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""Autoload built-in and out-of-tree backend libraries and registration hooks."""
+
+from __future__ import annotations
+
+import os
+import warnings
+from importlib.metadata import entry_points
+from pathlib import Path
+
+from tvm_ffi.libinfo import load_lib_ctypes
+
+from tvm.backend.loader import load
+from tvm.base import _LOADED_LIBS
+
+_BUILTIN_BACKENDS = (
+    "cuda",
+    "metal",
+    "rocm",
+    "trn",
+    "opencl",
+    "vulkan",
+    "webgpu",
+    "hexagon",
+    "adreno",
+)
+
+_AUTO_LOAD_DONE = False
+
+
+def _load_builtin_backends() -> None:
+    """Load all in-tree backend Python hooks."""
+    for name in _BUILTIN_BACKENDS:
+        load(name)
+
+    runtime_dir = Path(_LOADED_LIBS["tvm_runtime"]._name).resolve().parent
+    try:
+        # Load libtvm_runtime_extra if available for registration side effects.
+        _LOADED_LIBS["tvm_runtime_extra"] = load_lib_ctypes(
+            package="tvm",
+            target_name="tvm_runtime_extra",
+            extra_lib_paths=[runtime_dir],
+            mode="RTLD_LOCAL",
+        )
+    except (OSError, FileNotFoundError, RuntimeError):
+        pass
+    return None
+
+
+def _autoload_backends() -> None:
+    """Load built-in backends and invoke out-of-tree backend entry points."""
+    global _AUTO_LOAD_DONE
+    if _AUTO_LOAD_DONE:
+        return
+    _AUTO_LOAD_DONE = True
+
+    if os.environ.get("TVM_DEVICE_BACKEND_AUTOLOAD", "1") == "0":
+        return
+
+    from tvm import _RUNTIME_ONLY  # pylint: disable=import-outside-toplevel
+
+    if not _RUNTIME_ONLY:
+        _load_builtin_backends()
+
+    # Out-of-tree extensions opt into being loaded automatically at ``import tvm`` time
+    # by declaring an entry point in the ``tvm.backends`` group:
+    # [project.entry-points."tvm.backends"] tvm_foo = "tvm_foo:_autoload".
+    # Autoload can be disabled via ``TVM_DEVICE_BACKEND_AUTOLOAD=0``.
+    for entry_pt in entry_points(group="tvm.backends"):
+        try:
+            entry_pt.load()()
+        except Exception as e:  # pylint: disable=broad-except
+            warnings.warn(f"Failed to autoload tvm backend '{entry_pt.name}': {e}")